Internal-fault selective reclosingrelay



M81'42h4, 1947. g URN INTERNAL-FAULT SELECTIVE RECLOSING-RELAY Filed Feb. 29, 1944 WITNESSES: INVENTOR John L B/a ckbum,

ATTORNEY Patented Mar. 4, 1947 IN TERNAL-FAULT SELECTIVE RECLOSING- RELAY John L. Blackburn,.East Orange, N.-J., assignor'to Westinghouse Electric Corporation, East :Pittsburgh, Pa.,-a'corporation of Pennsylvania Application February 29, 1944, fSerialN'o. 524,348

14=Claims. 1

My invention relates to protective relaying systems for controlling the line-sectionalizing circuit-breakers at the two ends of a transmissionline section which is to be protected, or similar apparatus.

Heretofore, there has been a demand for an automatic reclosing system which would selectively reclose the circuit breakers immediately after an opening-operation as a result of an internal fault on the protected linesection, but not after an opening-operation as a result of an external fault elsewhere on the transmission system. Heretofore, however, a practical means for providing this feature, without considerable relay-redesign, has not been apparent, with the result that such internal-fault-responsive selective recicsing has not been generally provided, previcus to my present invention.

The object of my invention is to provide a practical selective reclosing-system of the type referred to.

With the foregoing and other objects in view, my invention consists in the apparatus, relays, circuits, systems, combinations and methods hereinafter described andclaimed, and illustrated in the accompanying drawing, the single figure of which is a diagrammatic view of circuits and apparatus embodying my invention in an illustrative preferred form of embodiment.

I have illustrated my invention as being applied to the protection of a three-phase transmissionline section I, which is connected .to a bus 2 through a circuit-breaker 3. The circuit-breaker is shown as being provided with a plurality of make-contact auxiliary switches ,4, -5 and 6, as well as a trip-coil TC, and a closing .coil CC. As the equipment at both ends of the protected linesection is similar, an illustration of the terminal equipment at only one end will sufiice.

Any kind of fault-locating protective relays may be utilized, for detecting and locating faults on the transmission line and for quickly initiating a tripping-operation of the circuit-breakers at both ends of the protected line-section, in case the fault is an internal fault, that is, within the protected line-section. Back-up protective relaying-means are usually provided, in combination with a timer, for causing a delayed trippingoperation in response to external faults, or in response to faults which, for any reason, are'not cleared by the quick tripping of some suitable circuit-breakers on the transmission line. The problem is, to provide a simple means for immediately automatically reclosing a tripped circuitbreaker if the"tripipng-operaticn was quick or in- (Cl. :-i2.94)

stantaneous, indicating the occurrence of an internal fault, but not'producing an automatic reclosing operation after time-delayed trippingoperations which indicate the presence'of an external fault. The automatic-selective reclosingoperation may-be performed either in response to all internal-fault indications, .or in response to any selected type or types-of internal-fault indications.

An illustrative type of fault-responsive relaying apparatus is illustrated in the drawing, in the form of three phase-relays, one .for each of the three line-phases A, 'B and C, only the phase-A relays being shownin detail. The relays comprise a-directional element D, and first, second, and third-zone impedance-elements Z4, Z2, and Z3. The operating coils and'therelay-contacts of the various relays are designated by the letter-designation of the respective relays. The directional element also has voltage coils which are indicated at Dv, and the three impedanceelements have voltage-restraint coils which are indicated under the general designation Zv. Current and voltage for controlling the various faultresponsive relays are supplied by means of linecurrent transformers ll], potential transformers H, and auxiliary current-transformers ii, in a known manner.

In accordance with my invention, 1 provide a latched-type selector-relay SX,-or any-other retainedposition relay, which automatically retains its position, even after the removal of the actuating energy whichcausedthe relay to move to that position. Itisxillustrated as having an actuating coil and ,a relay-contact, both of which are designated .by the relay-designation SK, and also alatch-operating or reset-coil SXL. Apositionretaining type of relay, SX, is needed,ofor safety reasons, because of the fact that most protective relaying systems require the useof'some kind of contactor switch CS, the operating coil of which isconnected in thetripping circuit, andzthe relaycontact of which is utilized to instantly bypass allof :the contacts of the efiective fault-respon: sive relays which areutilized to initiate the tripping function. An illustrative circuit-connection is shown in the drawing and will now be described in detail.

A plurality-of tripping circuits are provided, starting-with the negative-bus and all passing first through the directional-relay contact D, and thence to a conductor l5. From theconductor 15, an instantaneous first-zone tripping circuit is provided through the first-zone impedance-relay contact Z! to a conductor l5, thence through the operating coil SX to a conductor ii, and thence through the operating coil CS and the trip-coil TC to the auxiliary breaker-contact i and to the positive bus A second instantaneous tripping circuit is provided, from the conductor l5, through the second-zone impedancerelay contact Z2, to a conductor l8, and thence through a receiver-relay contact RR to the previously mentioned trip-circuit conductor H3.

The receiver-relay contact RR may be taken as being symbolic of any relay-contact which is responsive to a tripping designation or response at the far end of the protected line-section, so as to enable the Z2 element at the illustrated end to distinguish between faults which are closer than the far end of the line-section and those which are beyond it. The particular receiverrelay contact RR which is shown, for illustrative purposes, is a part of a known carrier-current system which will be subsequently described.

In addition to the two instantaneous or quickacting tripping circuits which have already been described, I have illustrated two time-delayed tripping circuits, for back-up protection, which are under the control of a timer TA having successive time-delay contact-points T2 and T3 respectively. The timer TA may be energized from a saturating current-transformer ST, which may be energized from the phase-A relayingcurrent, as indicated in the alternating-current connections. Operation of the timer is initiated by a Z3 contact 28, which is carried by the thirdzone impedance-element Z3. A second-zone time-delay tripping-circuit is provided, by connecting the T2 timer-contact between the tripping-circuit. conductors l8 and H which have been previously described. A third-zone timedelay tripping-circuit is also provided by means of a connection, from the tripping-circuit conductor I5, through the Z3 contact 20 and the timer-contact T3, to the previously mentioned conductor H.

The tripping-circuit conductor i8 is also utilized to energize the operating coil of an auxiliary relay CSP, which will be subsequently referred to.

A bypass tripping-circuit is provided from the negative bus through the contactor-switch contact OS, to the previously mentioned trippingcircuit conductor H.

The closing-circuit connections are controlled by my latched-relay contacts SX, which are connected between the negative bus and a backcontact 2i of an auxiliary latched relay H, and thence to a conductor 22, which is utilized to energize the operating coil of an auxiliary relay X, the circuit of which is completed through the back contact of a relay Y, and thence to the positive bus The relay Y may be provided with a dashpot 23 or other means for slightly delaying the pick-up action of this relay.

When the auxiliary relay X picks up, it energizes a holding-circuit through its first contact 2 5, which is connected between the negative bus and the conductor 22. The operating coil of the relay Y is energized from said conductor 22, through the auxiliary circuit-breaker contact 6, which closes when the circuit-breaker closes, the dash-pot 23 of the relay Y being intended to prevent the picking up of the auxiliary relay Y during the first instant of the circuit-breaker opening-operation, so that said relay Y does not pick up until the circuit-breaker 3 recloses again, or is nearly reclosed.

The auxiliary relay X has two other contacts 26 and 2'! which are utilized to energize the closing-coil CC of the circuit-breaker. In this manner, the closing-coil energization is initiated practically simultaneously with the initiation of tripping-circuit energization, but the electrical constants are such that the circuit-breaker opens, before the closing-coil CC gets into operation strongly enough to reverse the movement of the circuit-breaker mechanism and start the closingoperation. The X-relay contact 26 may also be utilized to energize the operating coil H of the auxiliary latch type relay, and also the latchreleasing or reset-coil SXL of my newly provided relay SX.

The auxiliary breaker-contact 5 is utilized, in series with a make-contact 30 of the auxiliary latch-type relay H, to energize the operatin coil of an auxiliary timer Tl, from any suitable circuit M, which may be a -volt alternatingcurrent circuit.

The timer-contact Tl is utilized to energize the latch-releasing or reset-coil 1-11, of the latch-type relay H, thus resetting the closing mechanism to its initial position, ready for another reclosingoperation.

When the auxiliary latch-type relay H is energized, by the X-relay contact 26, it not only closes its make-contact 30, the eiiect of which has been described, but it also opens its backcontact 2%, the eiiect of which is to lock out a subsequent attempt of the contact SX to reclose the breaker, ii the breaker-tripping circuit Iii should again be energized, to reopen the breaker. The H-relay back-contact 2i prevents reclosure unless the second energization of the trippingircuit occurs, or remains in effect, after the expiration of the time-delay introduced by the timer contact Tl, which resets the closin mechanism as described.

The carrier-current apparatus is indicated, at the bottom of the figure, as comprising a transmitter which is diagrammatically indicated at T, and a receiver which is diagrammatically illustrated at R, both being connected to a couplingtransformer iii which is coupled to the line-conductor C of the protected line-section 1 through a coupling-capacitor 42. The transmitter is indicated as having an oscillator-tube CS0, and the receiver is indicated as having a receiver-tube REC.

The transmitter-oscillation is initiated by a second Z3 contact A l, which is connected between the negative bus and a conductor 45. The transmitter-starting circuit is continued, from the conductor 55, through the back-contact CSP of the auxiliary relay CSP, to a conductor 41 which is connected to the cathode of the oscillatortube OSC. The conductor 47 is also connected, through a resistance Rl, to the positive bus so that, previous to the pick-up of the Z3 contact i l, the oscillator-tube OSC is blocked by havin its cathode connected to the positive bus through the resistor R5. The conductors $5 and 4'5 are also joined by a second circuit which includes the receiver-relay operatingcoil RR and a resistor R2. The plate or anode of the oscillator-tube OSC is energized through a tap-point 49 on a potentiometer 5B which is connected between the positive and negative buses, as shown.

The cathode of the receiver-tube REC is connected to a second tap-connection 5! of the potentiometer 5i], and this receiver-tube is utilized to energize a receiver-relay holding-coil RRH, in accordance with a known practice.

In operation, an internal fault will cause an energization of the tripping-circuit conductor l6 from the negative bus thus momentarily energizing my auxiliary latch-type relay SX, causing it to pick up in the moment before the bypassing contact of the contactor-switch CS short-circuits the operating-coil of the SX relay. This provides a closed SX contact which remains closed, notwithstanding the use of the bypassing trip-circuit contacts CS, whereby a selective breaker-closing operation may be made possible.

It will be noted that my auxiliary latch-type relay SX is not energized in response to external faults, which do not result in the energization of the trip-circuit conductor IE, but result in the energization of the trip-circuit conductor IT, as previously described.

The closing-circuit connections are initiated by the closure of the contacts SX of my auxiliary latched-type relay. From this point on, the closing operation is, or may be, a conventional one, and it is believed that its sequence of operations will be sufficiently understood, from the previous description of the closing circuits, without further explanation.

In like manner, the carrier-current control is, or may be, a conventional one. Carrier-current transmission is initiated in response to the Z3 make-contact 44, and it is removed or discontinued by an opening of the back-contacts CSP of the auxiliary relay CSP which is energized jointly in response to an internal-direction response of the directional relay D and a response of the second-zone impedance element Z2. At the same time when the CSP back-contact discontinues carrier-current transmission, it removes a shortcircuit from across the operating-coil of the re ceiver relay RR, thus conditioning the receiver relay to pick up as soon as its holding-coil RRH is deenergized as the result of the removal of the carrier-current from both ends of the protected line-section.

While I have illustrated my invention in a single preferred form of embodiment, I wish it to be understood that my invention is not limited to this particular embodiment, but is susceptible of various changes within the skill of the skilled workers of the art. I desire, therefore, that the appended claims be accorded the broadest construction consistent with their language.

I claim as my invention:

1. 'Terminal protective equipment for protecting a terminal of a transmission-line section, comprising the combination, with a line-sectionalizing circuit-interrupting means at that terminal of the line-section, of internal-fault-responsive relaying-means for selectively energizing an internal-fault trip-circuit conductor in response to an internal fault on the protected line-section, external-fault-responsive relaying-means for selectively energizing an external-fault trip-circuit conductor in response to an external fault elsewhere on the transmission system, a selector-relay having an operating-coil, circuit-means for connecting the operating-coil of the selector-relay between the two trip-circuit conductors, openingmeans energized from one of said trip-circuit conductors for eflecting an opening operation of said circuit-interrupting means, and closingmeans responsive to said selector-relay for efiecting a reclosing operation of said circuit-interrupting means only in the event of an energization of said internal-fault trip-circuit conductor.

2. The invention as defined in claim 1, in combination with contactor-means energized when said opening-means is energized from said one of the trip-circuit conductors for providing a bypassing energizing-circuit for said one of the tripcircuit conductors, said selector-relay being of the retained-position type, and means for reset ting the selector-relay.

3. Terminal protective equipment for protecting a terminal of a transmission-line section, comprising the combination, with a line-sectionalizing circuit-interrupting means at that termi-- nal of the line-section, of first and second linefault-responsive relaying-means for respectively energizing a first and a second trip-circuit conductor, a selector-relay having an operating-coil, circuit-means for connecting the operating-coil of the selector-relay between the two trip-circuit conductors, opening-means energized from the second trip-circuit conductor for effecting an opening operation of said circuit-interrupting means, contactor-means energized when said opening-means is energized from said second trip-circuit conductor for providing a bypassing energizing-circuit for said second trip-circuit conductor, closing-means responsive to said selector-relay for effecting a reclosing operation of said circuit-interrupting means only in the event of an energization of said first trip-circuit conduetor, said selector-relay being of the retainedposition type, and means for resetting the selector-relay.

4. Terminal protective equipment for protecting a terminal of a transmission-line section, comprising the combination, with a line-sectionalizing circuit-interrupting means at that terminal of the line-section, of internal-fault-responsive relaying-means for selectively energizing an internal-fault trip-circuit conductor in response to an internal fault on the protected line-section, external-fault-responsive relaying-means for selectively energizing an external-fault trip-circuit conductor in response to an external fault elsewhere on the transmission system, openingmeans for eiTecting an opening operation of said circuit-interrupting means in response to both of said trip-circuit conductors in such manner that said opening-means is energized whenever either one of said trip-circuit conductors is energized, and closing-means for effecting a reclosing operation of said circuit-interrupting means, said closing-means being selectively responsive to an energization of said internal-fault trip-circuit conductor, and being nonresponsive to an energization of said external-fault trip-circuit conductor.

JOHN L. BLACKBURN.

REFERENCES CITED UNITED STATES PATENTS Name Date Goldsborough et a1. Sept. 7, 1943 Number 

